Cancer is a major public health concern in the United States and around the world. It is estimated that over 1 million new cases of invasive cancer will be diagnosed in the United States in 1998. The most prevalent forms of the disease are solid tumors of the lung, breast, prostate, colon and rectum. Cancer is typically diagnosed by a combination of in vitro tests and imaging procedures. The imaging procedures include X-ray computed tomography, magnetic resonance imaging, ultrasound imaging and radionuclide scintigraphy. Frequently, a contrast agent is administered to the patient to enhance the image obtained by X-ray CT, MRI and ultrasound, and the administration of a radiopharmaceutical that localizes in tumors is required for radionuclide scintigraphy.
Treatment of cancer typically involves the use of external beam radiation therapy and chemotherapy, either alone or in combination, depending on the type and extent of the disease. A number of chemotherapeutic agents are available, but-generally they all suffer from a lack of specificity for tumors versus normal tissues, resulting in considerable side-effects. The effectiveness of these treatment modalities is also limited, as evidenced by the high mortality rates for a number of cancer types, especially the more prevalent solid tumor diseases. More effective and specific treatment means continue to be needed.
Despite the variety of imaging procedures available for the diagnosis of cancer, there remains a need for improved methods. In particular, methods that can better differentiate between cancer and other pathologic conditions or benign physiologic abnormalities are needed. One means of achieving this desired improvement would be to administer to the patient a metallopharmaceutical that localizes specifically in the tumor by binding to an enzyme or receptor expressed only in tumors or expressed to a significantly greater extent in tumors than in other tissue. The location of the metallopharmaceutical could then be detected externally either by its imageable emission in the case of certain radiopharmaceuticals or by its effect on the relaxation rate of water in the immediate vicinity in the case of magnetic resonance imaging contrast agents.
This tumor specific metallopharmaceutical approach can also be used for the treatment of cancer when the metallopharmaceutical is comprised of a particle emitting radioisotope. The radioactive decay of the isotope at the site of the tumor results in sufficient ionizing radiation to be toxic to the tumor cells. The specificity of this approach for tumors minimizes the amount of normal tissue that is exposed to the cytotoxic agent and thus may provide more effective treatment with fewer side-effects.
Previous efforts to achieve these desired improvements in cancer imaging and treatment have centered on the use of radionuclide labeled monoclonal antibodies, antibody fragments and other proteins or polypeptides that bind to tumor cell surface receptors. The specificity of these radiopharmaceuticals is frequently very high, but they suffer from several disadvantages. First, because of their high molecular weight, they are generally cleared from the blood stream very slowly, resulting in a prolonged blood background in the images. Also, due to their molecular weight they do not extravasate readily at the site of the tumor and then only slowly diffuse through the extravascular space to the tumor cell surface. This results in a very limited amount of the radiopharmaceutical reaching the receptors and thus very low signal intensity in imaging and insufficient cytotoxic effect for treatment.
Alternative approaches to cancer imaging and therapy have involved the use of small molecules, such as peptides, that bind to tumor cell surface receptors. An In-111 labeled somatostatin receptor binding peptide, In-111-DTPA-D-Phe1-octreotide, is in clinical use in many countries for imaging tumors that express the somatostatin receptor (Baker, et al. Life Sci., 1991, 49, 1583-91 and Krenning, et al., Eur. J. Nucl. Med., 1993, 20, 716-31). Higher doses of this radiopharmaceutical have been investigated for potential treatment of these types of cancer (Krenning, et al., Digestion, 1996, 57, 57-61). Several groups are investigating the use of Tc-99m labeled analogs of In-111-DTPA-D-Phe1-octreotide for imaging and Re-186 labeled analogs for therapy (Flanagan, et al., U.S. Pat. No. 5,556,939, Lyle, et al., U.S. Pat. No. 5,382,654, and Albert et al., U.S. Pat. No. 5,650,134).
There continues to be a need for more effective treatment options for patients with solid tumors. This is especially true in cases of metastatic cancer in which current standard chemotherapy and external beam radiation regimens only result in marginal survival improvements.
Although improvements in cytotoxic chemotherapeutics have been made in recent years, the toxicity of these compounds to normal tissues has continued to severely limit their utility in extending survival in patients with solid tumors. Recently developed combinations of different therapeutic modalities, such as external beam irradiation and chemotherapy (i.e. chemoradiation), has provided some incremental benefit to the control of tumor progression and quality of life. However, neither systemic chemotherapeutics nor external beam irradiation have acceptable therapeutic indices, and are often limited due to unacceptable toxicity to normal tissues. The concept of combined therapy of cancer using anti-angiogenesis drugs in combination with chemotherapeutics is not new. Further, the concept of combining targeted in-vivo radiotherapy using radiolabeled antibodies and antibody fragments with chemotherapy has been reported (Stein R, Juweid M, Zhang C, et al., Clin. Cancer Res., 5: 3199s-3206s, 1999). However, the combination of a angiogenesis-targeted therapeutic radiopharmaceutical which is targeted to receptors, which are then upregulated in the neovasculature of tumors, together with chemotherapy has not been described before. Therefore, there is a need for a combination of a therapeutic radiopharmaceutical, which is targeted to localize in the neovasculature of tumors, with chemotherapeutics or a radiosensitizer agent, or a pharmaceutically acceptable salt thereof, to provide additive or synergistic therapeutic response without unacceptable additive toxicity in the treatment of solid tumors.
The major advantage of combined chemotherapy and angiogenesis-targeted therapeutic radiopharmaceuticals, over each therapeutic modality alone, is improved tumor response without substantial increases in toxicity over either treatment alone. The advantage of using neovascular-specific radiopharmaceuticals, versus a tumor-cell targeted antibody, is that there is much lower systemic radiation exposure to the subject being treated.
Further, if the receptor targets for the radiopharmaceutical compounds, used in this method of treatment, are expressed on the luminal side of tumor vessels, there is no requirement that these compounds traverse the capillary bed and bind to the tumor itself.
Thus, it is desirable to provide a combination of angiogenesis-targeted therapeutic radiopharmaceuticals and a chemotherapeutics or a radiosensitizer agent, or a pharmaceutically acceptable salt thereof, which target the luminal side of the neovasculature of tumors, to provide a surprising, and enhanced degree of tumor suppression relative to each treatment modality alone without significant additive toxicity.
Matrix metalloproteinases (MMPs) are a family of structurally related zinc-containing enzymes that mediate the integrity of extracellular matrix (Whittaker, M. et al, Chem. Rev., 1999, 99, 2735-2776). They are excreted by a variety of connective tissue and pro-inflammatory cells, such as, fibroblasts, osteoblasts, macrophages, neutrophils, lymphocytes and endothelial cells. There is now a body of evidence that matrix metalloproteinases (MMPs) are important in the uncontrolled breakdown of connective tissue, including proteoglycan and collagen, leading to resorption of the extracellular matrix. This is a feature of many pathological conditions, such as rheumatoid and osteoarthritis, corneal, epidermal or gastric ulceration; tumor metastasis or invasion; periodontal disease and bone disease. Normally these catabolic enzymes are tightly regulated at the level of their synthesis, as well as, at their level of extracellular activity through the action of specific inhibitors, such as alpha-2-macroglobulins and TIMP (tissue inhibitor of metalloproteinase), which form inactive complexes with the MMPs. Therefore, extracellular matrix degradation and remodeling are regulated by the relative expression of TIMPs and MMPs. The MMPs are classified into several families based on their domain structure: matrilysin (minimal domain, MMP-7), collagenase (hemopexin domain, MMP-1, MMP-8, MMP-13), gelatinase (fibronectin domain, MMP-2, MMP-9), stromelysin (hemopexin domain, MMP-3, MMP-10, MMP-11), metalloelastase (MMP-12). In addition, the transmembrane domain family (MT-MMPs) has been recently discovered and comprises MMP-14 through MMP-17.
It has been established that MMP activity is elevated during tumor progression. MMPs mediate invasion and metastasis mostly by matrix remodeling, allowing tumor cells to access vessels. MMPs also play a role in primary tumor growth and may be involved in the release of stroma-bound growth factors and tumor angiogenesis (Summers, J. B., et al, Annual reports in Med. Chem., 1998, 33, 131). MMPs have been detected in cancerous tissue and the expression of a given MMP is not restricted to a specific tumor type. Correlation between tumor behavior and MMP activity in human cancerous tissues has been reported. Some MMPs, such as the gelatinases are particularly important in tumor progression.
Therefore, pharmaceuticals targeted to one or more MMP's would be very useful for detecting or treating cancerous tissue.
Ahrens, et al. U.S. Pat. No. 5,674,754 discloses methods for the detection of Matrix Metallo-Proteinase No. 9, using antibodies which selectively recognize pro-MMP-9 and complexes of pro-MMP-9 with tissue inhibitor of matrix metallo proteinase-1 (TIMP-1), with no substantial binding to active MMP-9. Venkatesan, et al. U.S. Pat. No. 6,172,057 discloses non-peptide inhibitors of matrix metalloproteinases (MMPs) and TNF-.alpha. converting enzyme (TACE) for the treatment of arthritis, tumor metastasis, tissue ulceration, abnormal wound healing, periodontal disease, bone disease, diabetes (insulinresistance) and HIV infection.
Pathologically, MMPs have been identified as associated with several disease states. For example, anomalous MMP-2 levels have been detected in lung cancer patients, where it was observed that serum MMP-2 levels were significantly elevated in stage IV disease and in those patients with distant metastases as compared to normal sera values (Garbisa et al., 1992, Cancer Res., 53: 4548, incorporated herein by reference.) Also, it was observed that plasma levels of MMP-9 were elevated in patients with colon and breast cancer (Zucker et al., 1993, Cancer Res. 53: 140 incorporated herein by reference).
Elevated levels of stromelysin (MMP-3) and interstitial collagenase (MMP-1) have been noted in synovial fluid derived from rheumatoid arthritis patients as compared to post-traumatic knee injury (Walakovits et al., 1992, Arth. Rheum., 35: 35) incorporated herein by reference. Increased levels of mRNA expression for collagenase type I (MMP-1) and collagenase type IV (MMP-2) have been shown to be increased in ulcerative colitis as compared to Crohn's disease and controls (Matthes et al., 1992, Gastroenterology, Abstract 661, incorporated herein by reference). Furthrmore, Anthony et al., 1992, Gastroenterology, Abstract 591, demonstrated increased immuno-histochemical expression of the gelatinase antigen in a rabbit model of chronic inflammatory colitis.
It has been shown that the gelatinase MMPs are most intimately involved with the growth and spread of tumors. It is known that the level of expression of gelatinase is elevated in malignancies, and that gelatinase can degrade the basement membrane which leads to tumor metastasis. Angiogenesis, required for the growth of solid tumors, has also recently been shown to have a gelatinase component to its pathology. Furthermore, there is evidence to suggest that gelatinase is involved in plaque rupture associated with atherosclerosis. Other conditions mediated by MMPs are restenosis, MMP-mediated osteopenias, inflammatory diseases of the central nervous system, skin aging, tumor growth, osteoarthritis, rheumatoid arthritis, septic arthritis, corneal ulceration, abnormal wound healing, bone disease, proteinuria, aneurysmal aortic disease, degenerative cartilage loss following traumatic joint injury, demyelinating diseases of the nervous system, cirrhosis of the liver, glomerular disease of the kidney, premature rupture of fetal membranes, inflammatory bowel disease, periodontal disease, age relatedmacular degeneration, diabetic retinopathy, proliferative vitreoretinopathy, retinopathy of prematurity, ocular inflammation, keratoconus, Sjogren's syndrome, myopia, ocular tumors, ocular angiogenesis/neovascularization and corneal graft rejection. For recent reviews, see: (1) Recent Advances in Matrix Metalloproteinase Inhibitor Research, R. P. Beckett, A. H. Davidson, A. H. Drummond, P. Huxley and M. Whittaker, Research Focus, Vol. 1, 16-26, (1996), (2) Curr. Opin. Ther. Patents (1994) 4(1): 7-16, (3) Curr. Medicinal Chem. (1995) 2: 743-762, (4) Exp. Opin. Ther. Patents (1995) 5(2): 1087-110, (5) Exp. Opin. Ther. Patents (1995) 5(12): 1287-1196, all of which are incorporated herein by reference.
The P3′ position is a relatively open area in the succinyl hydroxamates, and a wide range of substitutents, see for example (7), may be introduced (Sheppard, G. S. et al, Bioorg. Med. Chem. Lett., 1998, 8, 3251) at this position. This position also offers the flexibility of attaching a variety of linkers and chelators for diagnostic purposes.
Therefore, pharmaceuticals targeted to one or more MMPs would be very useful for detecting or treating diseases associated with MMPs.